I wondered in my post (here) last Friday why the daily growth in COVID-19 cases had stopped declining. I can thank my wife for the answer. It looks like a reporting issue. Weekends are under-reported, and the numbers catch-up during the week.
This is not surprising given the current demands on our health care system, and yesterday’s numbers highlight the situation (Figure 1). The USA has been on a steady case number growth trajectory since early March. The two most notable deviations occurred on Saturday March 21st and Sunday April 5th. Yesterday’s case number looks especially suspicious.
Figure 1 COVID-19 Daily USA Case Counts
Figure 2 shows the USA’s day/day change in case growth rate for the last 7 complete weeks. The pattern of rising, leveling and declining day/day growth rates is characteristic across the world as country’s take action to slow the spread of the virus and then bring its spread under control. In the USA, the one-week moving average shows that there has been a steady decline in growth rate since March 23rd. The daily decline in growth rate has averaged about 7% per day. Yesterday’s growth rate, if it holds, would favorably increase this value.
Figure 2 Daily Growth Rates for the Last 7 Weeks
Table 1 shows the daily day/day growth rate averages for each day of the week for the last 7 weeks. Saturday’s and Sunday’s are typically low, Monday’s are especially high, and the rest of the work-week averages on the high side.
Table 1 Day-of-Week Growth Rate Averages for the Last 7 Weeks
We’ll see what happens with today’s numbers. Even if they adjust upwards, the good news is that the 7% day/day decline should cause the daily case count to peak in the middle of April.
Reference
worldometers.info